1. Field of the Invention
The present invention relates to a light guide plate for use in a liquid crystal display; and more particularly to an improved light guide plate having enhanced light diffusion on a light output surface thereof, for use in a backlight system or a front light system of a liquid crystal display. This application relates to a contemporaneously filed application having the same title, the same applicants and the same assignee with the instant application.
2. Description of Prior Art
Liquid crystal materials cannot intrinsically emit light. Rather, a liquid crystal display must be equipped with an external light source. The so-called external light source is namely a backlight system or a front light system, which is used in conjunction with the liquid crystal display. A typical backlight or a front light system comprises a light guide plate for converting a point light source or a linear light source into a planar light source.
FIG. 5 shows a conventional back light system 1 for a liquid crystal display. The back light system 1 includes a linear light source 11, a cover 111 arranged around the linear light source 11, a light guide plate 12, a reflector 13, a diffuser 14, and two pieces of prism sheets 15. The light guide plate 12 is for re-directing light beams in order to achieve efficiency of light utilization and uniformity in luminance. However, the back light system 1 employing the light guide plate 12 must also employ a number of additional complementary elements such as the diffuser 14 and the prism sheets 15. This results in high manufacturing costs and unduly complicated assembly procedures.
FIG. 6 illustrates a light guide plate 2 as disclosed in Japan laid-open patent publication no. 07-020466. The light guide plate 2 has a wedge-shaped structure; and comprises an input surface 21, an output surface 22, and a bottom surface 23 opposite to the output surface 22. An array of prisms 24 is formed on the output surface 22. A distribution density of the prisms 24 gradually decreases with an increasing distance away from a light source (not shown). However, an additional lens sheet still needs to be employed in order to improve the light utilization and uniformity in luminance of the outgoing light from the output surface 22. Therefore, the light guide plate 2 has limited efficacy in decreasing the number of elements in the overall system.